A program of research is proposed focusing upon behavioral and biobehavioral investigations of mental retardation and intellectual development. The basic problem to be investigated is the general area of learning and its facilitation. Major areas of concentration include studies of the development of learning and memory processes, language, social interactions, methods of teaching, early experience, and prenatal stress. The ultimate objective is to identify and develop strategies and procedures for enhancing the adaptation of retarded persons to normal living circumstances. A related goal is to contribute to theories and the body of data concerning cognition, learning, and human development, with particular reference to the role of individual differences. The program is organized into three laboratories or research groups: Cognitive Processes, Comparative/Development, and Experimental Analysis. A wide variety of research strategies are followed including basic laboratory experiments, observational studies in natural contexts, intervention or training procedures, longitudinal investigations, and single-subject experiments. Subjects for investigation are at-risk and normal babies, retarded people at all functional levels, peers and parents of retarded children, and infra-human animals including rodents and primates. Among the specific topics to be investigated are: Perceptual development in normal and retarded children and babies, information processing capabilities among normal and retarded individuals, organization of semantic memory, patterns of infant-parent interactions, social interactions among retarded and normally developing children, analysis of discriminative and maintaining stimuli for aberrant and social responding, transfer or generalization of training, methods for teaching positive social behavior, receptive and productive language, imitation learning, establishment of basic stimulus control, effects of prenatal stress on behavioral and establishment of basic stimulus control, effects of prenatal stress on behavioral and physical development, and the effects on performance of motivation.